Beam Me Up: A Look At The Dimond Tri Bike

Dimond has revived an old bike design that can significantly reduce drag.

December 23, 2014 Aaron Hersh

Photo: John David Becker

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Dimond has revived an old bike design that can significantly reduce drag.

A quick history lesson: For more than a decade, Softride successfully made beam bikes that were raced by top pros—including one-time Kona bike record holder Jürgen Zack—and sold in many tri shops across the country. Then they went out of business, and the beam bike basically disappeared.

The idea of the beam bike was to eliminate the seat tube and chainstays to provide an opportunity to reduce aero drag and road vibration, but versions in the early 2000s were flawed and couldn’t compete with the first wave of truly exceptional carbon tri bikes. Much like neon colors, beam bikes are back after a decade away. Composites expert David Morse left Zipp’s advanced design engineering group to team up with Ironman pro T.J. Tollakson to create a modernized beam bike that is functionally equivalent to the top current tri bikes, yet faster. Their creation—called the Dimond—is not only fast but also extremely practical.

RELATED – T.J. Tollakson: The Idea Man

Designing the Dimond

As a tiny startup, Dimond didn’t have the funds to test a set of designs and pick the fastest one. Morse used his extensive aero experience to dream up the most efficient frame he could, then took it to the wind tunnel to see how he had done. This isn’t the ideal way to build a bike. With a bigger budget, Morse and Tollakson could have created an even faster design with the help of CFD and a wind tunnel. Eliminating the rear portion of the bike increases their margin for error, however. Through their own tests (with a legitimate and fair protocol), Dimond’s creators assert its frame tested faster than the two elite tri bikes Morse put through the same test at the Faster Wind Tunnel in Arizona.

Ride Feel
First and most importantly: This bike doesn’t bob. Some older beam bikes with a metal appendage have an annoying habit of bouncing up and down in sync with the pedal stroke. Riding the Dimond is solid and stable, in stark contrast to those bikes. It feels like riding a normal frame, but a little bit smoother. It still responds to steering input from the hips and moves as predictably as a typical tri bike. Ride feel is one of the Dimond’s biggest triumphs.

Accessories
There isn’t a single bottle mount on this frame. All accessories must be carried by aftermarket systems. While this method keeps the bike streamlined, it limits the options for a rider. Bringing more than one bottle requires a rear carrier.

Mechanical Ease
Despite looking as eccentric as any integrated super-bike, the Dimond is deceivingly simple mechanically. Cable routing isn’t overly complicated; saddle adjustments are a cinch; moving the aerobar is easy and even removing the beam for travel requires tinkering with just one bolt. Keeping this bike in top working order is surprisingly easy.

Handling
Riding in the aerobars feels secure and stable. The bike wants to hold a straight line and never feels wobbly or loose, even when reaching into a jersey pocket. It evenly tracks a swooping line through technical descents but isn’t quite as quick as some bikes when quickly changing course.